A study of the role of immune factors in Streptococcus faecalis pyelonephritis in rats is in progress. A graft versus host reaction was sought by injection of lymphocytes from pyeonephritic rats under the kidney capsule of normal syngenic rats. Although minor histologic reactions were noted they did not differ significantly from those induced with normal lymphocytes. On the other hand we have demonstrated delayed hypersenstivity of lymphocytes to normal kidney antigen and bacterial antigen by migration inhibition technique. We will continue immunologic studies with injection directly into the medulla by experiments designed to evaluate the role of T, B and K lymphocytes, circulating antibody and deposited bacterial antigen. We will further study these same factors in vitro. Role of immune factors will also be evaluated by studying the effect of immunosuppression on bacteriologic and histologic findings in S. faecalis pyelonephritis. We have found that injection of iron has a variable effect on severity of pyelonephritis in mice with different bacteria. We propose to study its effect on S. faecalis pyelonephritis and on pathogenicity of S. faecalis L-forms. In addition, a long term study of Escherichia coli pyelonephritis will be done with a strain that responded markedly to iron in early experiments. BIBLIOGRAPHIC REFERENCES: Kalmnson, G. M., Harwick, H. J., Turck, N., Guze, L. B. Urinary tract infection: Localization and virulence of Escherichia coli. Lancet I (7899), 134-136, Jan 1975. Kalmanson, G. M., Glassock, R. J., Harwick, H. J., Guze, L. B. Cellular immunity in experimental pyelonephritis. Kidney International S35-S43, 1975.